EP-A-0 959 076 discloses a device for hydrodynamic entwining for preferably binder-free compaction of the fibers of a fiber web of natural and/or artificial fibers of any type. It consists of
a) a first continuous belt which supports the fiber web and which is routed under tension between at least two rollers and is deflected,
b) a permeable needling drum which is looped by the continuous belt,
c) a second continuous belt which is likewise routed under tension between at least two rollers being assigned in the opposite direction to the first continuous belt; the working side of the second belt which is opposite the working side of the first continuous belt turns driven in the same direction as that of the first continuous belt, furthermore,
d) the two working sides of the two continuous belts in their lengthwise extension at the inlet are pointed conically towards one another so that the fiber web which lies on the working side of the first continuous belt is increasingly compressed between the continuous belts which are running ahead,
e) the two continuous belts are pressed by the two rollers against the needling drum for stronger looping of the drum and
f) between these two rollers a nozzle bank for wetting of the fiber web is pointed against the fiber web which is held compressed between the two continuous belts.
A device of this type has the advantage that the fiber web which runs ahead in terms of bulk is compressed increasingly slowly between the two continuous belts and with uniform pressure from the top and bottom without shear stress and only when it is held securely between the two continuous belts is it wetted on the needling drum. The nonwoven is pressed more strongly against the needling drum by the two rollers in front of and behind the nozzle bank. This stronger compression, or more correctly, the better holding of the fibers of the fiber web during wetting prevents floating of the individual fibers and ultimately leads to a better nonwoven product.
The device has proven itself in practice, it is characterized especially by intensive wetting which is produced uniformly on the drum, and then after diversion of the second from the first continuous belt, by needling which is still possible on the drum by means of a second nozzle bank which is now pointed directly against the fiber web which lies on the drum. But the construction is very complex and too expensive for many products. The object of the invention is a simpler construction which meets the same conditions.
To achieve this object, the invention calls for a device for hydrodynamically exposing the fiber web to a fluid for preferably binder-free compaction of the fibers of a fiber web of natural and/or artificial fibers of any type, which consists of
a) a first continuous belt which supports the fiber web and which is routed under tension between at least two rollers and is deflected,
b) a second continuous belt in the opposite direction which is likewise routed under tension between at least two rollers and which is assigned to the first continuous belt; the working side of the second continuous belt which is opposite the working side of the first continuous belt turns driven in the same direction as that of the first continuous belt,
c) the two working sides of the two continuous belts in their lengthwise extension at the inlet being pointed conically towards one another so that the fiber web which lies on the working side of the first continuous belt is increasingly compressed between the continuous belts which are running ahead,
d) a first nozzle bank which is assigned to the two continuous belts which turn with one another for wetting of the fiber web, for example, and
e) preferably in the case of using the device also as a compaction unit following this belt compacting unit, at least one more nozzle bank which is assigned directly to for example a continuous belt which continues to run with the fiber web lying thereon, and
f) the first continuous belt especially in the area of the first nozzle bank being pressed by at least one additional deflection roller against the directly assigned side of the second continuous belt or vice versa the second being pressed against the first continuous belt for stronger contact pressure of the two continuous belts which are running ahead with one another.
This device makes it possible to increasingly press and thus compact the nonwoven to be wetted between the continuous belts and then also continue to hold it securely, similarly to the device as claimed in EP-A-0 959 076. Therefore, what matters here is slow compacting and fixing, holding securely preferably even thin nonwoven between the belts during exposure to the first water jets. This is given in the device known beforehand, where the continuous belts in water needling are pressed against the needling drum. In this new device the needling drum is omitted and needling takes place more easily only between the two working sides of the continuous belts. They can however yield to the pressure of the water jets. To solve this problem, the continuous belts in the area of the nozzle bank must be held in an exactly guided manner. This can be achieved with only one or better two additional deflection rollers.
The objective in the addition to the device as claimed in the invention is achieved when this additional deflection roller for the two continuous belts is shifted into the plane of the side which is running ahead such that on the latter, depending on the desired contact pressure, a looping angle which is larger or smaller for the continuous belts is formed. Therefore it must be greater than 1 degree and in practice is between 5 and 35, up to 45 degrees.